Construction of multi-storey buildings

Abstract

A multi-storey building frame is constructed by manufacturing portal frames off site and transporting them to the site and erecting them to form a high precision building frame in an accurate manner. The method involves placing a series in a longitudinal direction of portal base frames, the base frames each having a pair of opposed wall frames, a structural ceiling frame, and a lower tie or structural frame spanning the wall frames at or near ground level. Sheeting is secured across the tops of the base frames. A series of portal top storey frames is placed over the sheeting to form a frame for a top storey and a roof, each said top storey frame comprising: a pair of opposed wall frames, a roof truss, and a lower tie or structural frame.

Description

[0001] Construction of Multi-storey Buildings

[0002] Introduction

[0003] The present invention relates to construction of multi-storey buildings, especially for residences or smaller buildings for commercial use, preferably buildings with maximum dimensions of up to about 15 m wide by 50 m long by 15 m high.

[0004] Multi-story buildings up to 3 stories in height are becoming more common as the construction industry looks to densification to help provide additional accommodation. These building are commonly built with steel, concrete, or wood, or a combination of the three materials. Common wood frame construction methods and techniques are stick-framing, modular construction, or prefabricated / panelised construction. Multi-story buildings are subject to increased design and structural complexity due to the higher required load-bearing capacity, wind resistance, people / live loading and seismic resistance.

[0005] The increased complexity of constructing multi story buildings traditionally impacts the entire design and build process due to factors such as the requirement for intricate framing with multiple load paths, large and heavy expensive components such as steel or engineered wood beams, complex foundation design requiring precision excavation, intensive steel forming, higher strength / specialized concrete or in the case of steel / wood piling a more complex and expensive design. There is often a need for large beams to carry upper floor loads in order to create openings on the lower floor(s), and a need for increased skills required to ensure all structural and infill framing elements are measured, cut, treated and installed correctly. Also, there are often a mix of materials requiring connection, introducing specialist engineered joints. The building height introduces more complexity when external and internal live loads are considered. These include wind, earthquake and people loads. The separate construction elements used to form the exterior envelope are required to create a continuous structure across both the vertical and horizontal planes as well as resisting seismic and live ‘vibration’ loads. The complexity of forming these multi-plane connections on site introduces additional cost, risk and time to construct. These connections are critical, and mistakes can cause catastrophic failure. Noncritical (precision or design) errors can result in rework and significant material waste. The interior of the multi-story building needs to account for sound transmission and vibration between floors to ensure that the movement of a larger number of people is mitigated. The mechanical and electrical systems used in multi-story buildings are much larger and more complex, typically located on one floor and required to be interconnect to the rest of the structure. This requires more space to accommodate these services, which increases the likelihood of structural elements being drilled or compromised. The large system requirements also reduce the space for continuous insulation.

[0006] Stick framing a multi-story building is very labour intensive and expensive. Also, modular or prefabrication of multi-story buildings relies on the presence of a local factory with the capacity to produce complex multi-story units. Moreover, prefabrication or modular factories do not use a standardized method of construction, resulting in highly individualized design. These complex designs use and EOD Engineered on Design approach which is slow and expensive.

[0007] The present invention is directed towards achieving a faster and less complex way to construct a prefabricated multi-story building.

[0008] Summary of the Invention

[0009] The invention provides a method of constructing a multi-storey building frame as set out in claim 1, and optional steps as set out in claims 2 to 20, a kit for such a method as set out in claim 21, and another method as set out in claim 22.

[0010] We describe a method of constructing a multi-storey building frame comprising the steps of: placing a series in a longitudinal direction of portal base frames in vertical position, at least some of the base frames each comprising: a pair of opposed wall frames, a structural ceiling frame, and a lower tie or structural frame spanning the wall frames at or near ground level; securing horizontal sheeting to the base frames across the tops of the base frames; interconnecting at least some of said base frames in the longitudinal direction by strongback braces, placing a series in the longitudinal direction of portal top storey frames over the sheeting in vertical position to form a frame for a top storey and a roof, each said top storey frame comprising: a pair of opposed wall frames, a roof truss, and a lower tie or structural frame spanning the wall frames; and interconnecting at least some of said top storey frames in the longitudinal direction by strongback braces.

[0011] In some preferred examples, opposed wall plates are secured to the sheeting and the top storey frames are placed on and span said wall plates.

[0012] In some preferred examples, each wall plate comprises a pair of parallel rails.

[0013] In some preferred examples, the base frame frames are interconnected by strongback structural members.

[0014] In some preferred examples, the top storey frames are interconnected by strongback structural members.

[0015] In some preferred examples, the top storey frames form a second storey or a mezzanine and they are placed directly on said sheeting.

[0016] In some preferred examples, an intermediate storey is formed by placing intermediate frames on said sheeting, interconnecting said intermediate frames in the longitudinal direction, and placing the top storey frames on said intermediate frames.

[0017] In some preferred examples, each of the base frame wall frames comprises a plurality of studs and at least one brace.

[0018] In some preferred examples, there is at least one intermediate stud in at least some base frame wall frames.

[0019] In some preferred examples, at least some of the top storey frame wall frames each comprises a plurality of studs and at least one brace.

[0020] In some preferred examples, the method comprises the further steps of pouring a concrete base on a foundation, placing a pair of opposed wall plates on the concrete base, and the base frames are placed on the concrete base and are secured to the wall plates.

[0021] In some preferred examples, each wall plate on the concrete base comprises a pair of rails. In some preferred examples, a space for a stairwell is provided by choosing a desired longitudinal spacing between two successive base frames to accommodate the stairwell.

[0022] In some preferred examples, cross members are secured to at least some of the intermediate frames before erection of the top storey frames.

[0023] In some examples, at least some base frames are each provided joined to an upper frame, either an intermediate frame or a top frame, by hinges, and they are folded to be co-planar on site.

[0024] In some examples, the method comprises the further steps of erecting on site at least two multistorey building frames laterally arranged side-by-side, with adjoining wall frames forming a party wall frame.

[0025] In some examples, the wall frames which form the party wall frame have less bracing than wall frames for an external wall.

[0026] In some examples, at least some adjoining structural members of adjoining frames are joined by spanning nail plates.

[0027] In some examples, at least one pair of upper and lower adjoining frames one atop the other are joined by a hold down bracket with an L-shaped nail plate and a bolt extending vertically through the nail plate, a structural member of one frame, and a structural member of the adjoining frame.

[0028] In some examples, said bolt extends through sheeting over the lower frame.

[0029] We also describe a kit comprising elements used in the methods described herein in various examples to construct a building frame.

[0030] In some preferred examples, the kit comprises: a plurality of portal base frames, at least some of the base frames each comprising: a pair of opposed wall frames, a structural ceiling frame, and a lower tie or structural frame spanning the wall frames at or near ground level; horizontal sheeting configured to fit to the base frames across the tops of the base frames; a plurality of portal top storey frames to form a frame for a top storey and a roof, each said top storey frame comprising: a pair of opposed wall frames, a roof truss, and a lower tie or structural frame spanning the wall frames.

[0031] We also describe a method of constructing a two-storey building frame comprising the steps of:

[0032] (a) placing a series in a longitudinal direction of portal base frames in vertical position, at least some of the base frames each comprising: a pair of opposed wall frames, and a lower tie or structural frame spanning the wall frames at or near ground level;

[0033] (b) either before or after step (a) folding out around hinges a portal top storey frame from each base frame to form a frame for a top storey and a roof, each said top storey frame comprising: a pair of opposed wall frames, a roof truss, and a lower tie or structural frame spanning the wall frames; and

[0034] (c) interconnecting at least some of said base frames in the longitudinal direction by strongback braces and interconnecting at least some of said top storey frames in the longitudinal direction by strongback braces.

[0035] Detailed Description of the Invention

[0036] The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings in which:

[0037] Figs. 1(a), (b), (c), (d), (e), and (f) are front views of frames which are used in various embodiments of the invention,

[0038] Figs. 2 (a), (b), (c), (d), (e), and (f) are perspective views showing stages of construction of a building gin one example,

[0039] Figs. 3 (a), (b), (c), and (d) are front views of different examples of buildings constructed in accordance with the invention,

[0040] Fig. 4 is a front view of an alternative multi-storey building constructed according to the invention, and Figs. 5(a) and (b) illustrate interconnection of frames in the factory for convenient and compact transport to site, Fig. 6 is a front view of frames for a terrace of multi-storey buildings with two vertical structures erected laterally of each other, and

[0041] Fig. 7 is a front view of a further multi-storey building frame, and Fig. 8 is an enlarged view showing joining of stud members at the interface of two frames.

[0042] We describe construction of a multi-story building using offsite manufactured truss portal frames There is a process of stacking the truss frames to form a building 1.5 or more stories in height, assembled on site or assembled into units in an offsite facility and later moved to site. A first level of truss frames forms the lower level, and a second set of pre-manufactured truss portal frames is erected to form a mezzanine floor or top floor incorporating roof truss members. As described below there may be an intermediate floor between the lower level and the top level.

[0043] In one example, initially there is provided a foundation, and a base plate is mounted to the foundation at the location of the side walls, the base plate or plates extending in a longitudinal direction. Base frames are placed on the base plates in succession at desired longitudinal interframe spacings, while temporarily supporting them to keep them at a vertical orientation.

[0044] The base frames are interconnected by sheets of planar material which span all of the base frames across the tops of these frames. These sheets may be plywood of OSB (oriented strand board) for example. The planar sheeting is fixed to the base frames spanning multiples of them, and then the top story (or mezzanine) is constructed by placement of a series of top storey frames on this sheeting base or wall plates on this sheeting base. The top storey frames incorporate a roof truss. Openings for stairwells for example are easy to incorporate between the frames as frames can be placed further apart with minor design amendment.

[0045] In some cases, if more than two storeys are required there is an intermediate storey formed by wall frames erected on the sheeting and then the top storey frames are erected on these wall frames. There may be a continuous top plate secured in place to span the tops of the intermediate wall frames, and the top storey frames are erected over this sheeting. In many examples the intermediate storey can be formed by a frame having structural side wall frames and preferably also a structural ceiling frame.

[0046] In some cases, frames are manufactured with a hinge between an upper frame and a lower frame. In some examples a plurality of building or building units are constructed by repeating the method steps to provide another multi-structure laterally alongside a first multi-structure, to provide for example a terrace.

[0047] Detailed Examples

[0048] Referring to Fig. 1 examples of frames used in the construction method are shown, as follows: Fig. 1(a), a base frame 1 with side wall frames 2 and 3 each having a pair of uprights 6 and 7 and a brace 8; a structural ceiling 4; and a ground level tie 5 linking the wall frames 2 and 3. This is suited to mounting to a level concrete base with a pair of wall plates.

[0049] Fig. 1(b), a base frame 11 with wall frames 12 and 13 also having a pair of uprights and a brace, a ceiling structural frame 14, and a ground level frame 15. Due to the structural ground level frame 15 these base frames may be mounted on piles.

[0050] Fig. 1(c), an open second storey frame 21. This has a pair of side wall frames 22 and 23, each again having a pair of uprights and a brace. There is a tie 25 across the lower parts of the wall frames 22 and 23, and a roof truss 25 across the top parts.

[0051] Fig. 1(d), a second story frame 31 having a pair of opposed wall frames 32 and 33, a roof truss 34 across the top and a structural floor frame 35 across the bottom.

[0052] Fig. 1(e), a mezzanine frame 41 with a pair of opposed wall frames 42 and 43, a roof truss 44 across the top and a tie 45 across the bottom.

[0053] Fig. 1(f) intermediate frame 51, again having a pair of uprights and a brace, being configured to form a wall when placed in series.

[0054] Any of the frames 1, 11, 21, 31 can be used also to erect a single level building. This may be convenient for a complex of multiple buildings, not all of which are multi-storey.

[0055] Two Storey Construction

[0056] The above frames may be used in different combinations according to the building design and conditions. As shown in Fig, 2(a) in one example a concrete base 101 is poured on a foundation, and as show in Fig. 2(b) a pair of opposed parallel wall plates 102 are secured in position. Fig. 2(c) shows a base frame 1 placed across the wall plates 102, and this is repeated until a series in the longitudinal direction of the base frames 1 are placed and inter-linked for support.

[0057] As shown in Fig. 2(d) sheets of wood 103 are secured in place to span the base frames 1 in order to form a rigid structure. Opposed wall plate pairs 104 are placed on the sheeting 103, as shown in Fig. 2(e). Top (in this case, second) storey frames 21 are placed in series on the second storey wall plates 104 to provide the second storey, as shown in Fig. 2(f).

[0058] An advantageous aspect is the installation of the sheeting 103 across the entire lower or base frame system to create a rigid structural plane. There is installation of strongbacks through the full length of the frame to introduce continuous bracing, providing more structural strength than is added by the sheeting 103. Brackets connect each frame to the base plate.

[0059] The double continuous base plates 104 on top of the sheeting 103 provide an excellent foundation for the top storey. Continuous strongbacks are added to the upper-level frames 21, and brackets are used to help secure the top storey frames. The building is closed in with structural sheeting to enclose the envelope.

[0060] The temporary cross ties 25, if present, are removed and the building is finished as per standard construction according to the building design. The present invention is concerned with providing the building frame, but not the manner in which the building is finished. However, it will be appreciated that the arrangement of the base and top storey frames provides for easy installation of services and insulation in the walls and roof.

[0061] In the example illustrated each wall frame has an outer stud 6, an inner stud 7, and a brace 8 between them. In various examples, the wall frames of at least some base frames each comprises at least one outer stud, at least one inner stud, at least one floor plate member interconnecting the outer and inner studs, and at least one diagonal brace between the outer stud and the inner studs. There may be an intermediate stud between the inner and outer studs, and there may be two braces, one between the outer stud and the intermediate stud and one between the intermediate stud and the inner stud. In some examples, there is a gap between the inner stud and the intermediate stud sufficient to provide a space for insulation when the primary frames have been erected.

[0062] In some examples, the method comprises the further step of pouring a (non load bearing) concrete floor after erection of the base frames. In some examples, the method comprises the further step of fixing at least one three-dimensional bracket to the slab, a base plate, and a primary frame.

[0063] Fig. 3(a) shows an end view and a side view of a building frame with base frames 11 and second storey frames 21, as described above. Use of Strongbacks as Bracing Members

[0064] There is excellent wind resistance in the lateral direction due to the advanced structural nature of portal frames, the wall frame, ceiling structure or integrated roof truss, and then the opposite wall frame. For wind resistance in the longitudinal direction wall sheeting, structural sheeting 103 and the strongbacks provide most resistance. Strongbacks are structural members extending generally in the longitudinal direction from one base frame and / or top storey frame to the next. They may be horizontal or alternatively at an angle to provide additional bracing strength. Strongbacks are common in roof truss design but cannot be applied to the walls in the case of a traditional wood frame building system. In the case of a truss portal framed building of the invention the use of the strongbacks as structural bracing members in the roof, wall and floor structure provides for a rapid and simplified method of introducing significant frame stiffness / resistance to racking.

[0065] In a medium wind zone strongbacks might be placed every 2 m to provide rigidity easily. In a very high wind load or earthquake zone they might be placed every 1 m, and preferably at floor, ceiling and roof levels. A simple structural analysis is produced for each a specific project to determine the number of bracing members (“strongbacks”) between each juxtaposed pair of frames and the spacings in the longitudinal direction. For example, there may be three strongbacks between floor and ceiling level in the opposing wall of the lower unit, with four strongbacks in the intermediary floor / ceiling in tandem with the floor sheeting 103 to resist the increased vibration from live loads. There may simultaneously be applied four strongbacks in the upper unit wall where there exists more wind due to buffering. In traditional construction these types of high load cases typically result in a labour-intensive process of resisting the racking of the building by introducing small segments of wood between the studs (“nogs” or “noggins”) which increases time, cost, and thermal bridging.

[0066] Further to this in extreme wind or earthquake conditions the most common point of failure in traditional construction is the joint between the Tower wall and the floor’ and the ‘upper wall and the roof truss’. The effect of the ‘roof being ripped off’ or the ‘roof and walls’ to lift off the floor and collapse. In the case of the inventio the introduction of the engineered truss plates in these locations can be significantly augmented by the presence of longitudinal strongbacks.

[0067] Three Storey Construction

[0068] Referring to Fig. 3(b), a building frame is constructed from a series in the longitudinal direction of a selection of the frames as follows.

[0069] Base frames 11, each of which incorporates a structural floor frame 15. Intermediate (or second) storey opposed wall frames 51. Each intermediate frame 51 is placed upright on the sheeting 103 and held in place by temporary braces.

[0070] Frames 31 placed in series on top of the intermediate frames 51. These form the top storey in a manner akin to the frames 21 forming the top storey of a two-storey building, but in this case, there is an intermediate storey formed by the series of opposed intermediate frames 51. These form the walls of the second, intermediate storey. There is sheeting 103 over the intermediate frames also.

[0071] It will be appreciated that the construction of a building frame in this case follows on the same techniques as for a two-storey frame, but with the additional steps of providing the intermediate frames for a second floor.

[0072] Referring to Fig. 3(c), another three-storey building frame is erected using a series of the base frames 1 (without a structural floor frame), second storey opposed wall frames 51, and third storey frame 31. The concrete 101 forms the structural floor and the base frames are prevented from kick out due to connection to the inner base plate 102. The temporary tie 5 holds it during construction.

[0073] As will be appreciated, the wall frames provide a simple means of achieving an intermediate storey between a base frame and a top frame with a roof truss.

[0074] Mezzanine Floor Construction

[0075] Fig. 3(d) shows another example of a two-storey building frame, in this case having base frames 11 and second storey frames 41, which form a mezzanine, not a full top floor.

[0076] Each base frame and top storey frame is a portal frame which is premanufactured and designed as a lower or upper unit. The frames when interconnected as described provide streamlined load paths across all levels with a distributed load to the outside edge of the foundation, eliminating the need for complex interior post and beam supports and complex foundation structure.

[0077] The connections across vertical and horizontal planes are manufactured in the factory, reducing time, cost, engineering requirements, and margin for error. The wall members provide for construction of wide walls of integrated structural members for ease of building servicing, insulation, and resistance to wind / seismic / vibration. The series of portal frames (base and top storey frames) form webs with strongbacks, achieving excellent structural rigidity and resistance to racking. Because only frames are required, offsite manufacture is simple and is of a type which can readily be done in many locations. The frames may be readily manufactured in factories already involved in supplying the construction industry with for example, roof trusses. Using local materials and eliminating the need to use steel and mass concrete foundations reduces the embodied carbon of the structure and allows for a cost effective and sustainable design outcome. The universal availability allows for repeatable designs across regions and countries.

[0078] On Piles

[0079] In another example, the base frames have a structural floor, providing sufficient structural strength to allow the base frames to be mounted to piles, in a manner as described for example in W02020 / 206526. Each base truss has a horizontal structural floor element extending between and connected to the vertical supports at floor level, the structural floor element being configured to engage a building foundation.

[0080] The vertical supports may have laterally spaced-apart vertical struts, and at least one diagonal brace between the vertical struts. In some cases, a lower first diagonal brace joins the struts at floor level, and at least one upper diagonal brace joins the struts above the first brace.

[0081] Preferably, the structural floor comprises a top beam, a bottom beam, and internal support structural members between said beams, and it preferably comprises a series of uprights and diagonal braces.

[0082] Referring to Fig. 4 a building frame 200 is provided by a base frame which is an inverted frame 1, with the structural ceiling 4 now acting as a structural floor and this frame rests on three floor plates 203. In this case the tie 5 can remain in place and provide sufficient structural support for the top frame 41 (in combination with its roof structural members 44) to be placed on top to provide a mezzanine. There is no need for sheeting between the base and the top frames, and they are in this case joined by hinges 201 so that they can be transported from the factory folded over. However, sheeting may be used, with gaps to accommodate the hinges. The hinges allow them to be opened out to be co-planar as shown in Fig. 5(b) on site in a manner whereby they are perfectly aligned and tied together. This arrangement is suited to low multi-storey buildings, with the second, top, storey being a mezzanine or the like. The hinged arrangement allows particularly convenient off-site manufacture, transport, and erection on site.

[0083] Terraced House Construction Referring to Fig. 6 two multi-storey buildings 250 are erected alongside each other to provide a frame for a terrace. Each building comprises a base frame 252, an intermediate frame 253, and a top frame 254. Each of these frames has a structural ceiling frame and sheeting on top of the base and intermediate frames. However, in this case the frames have structural wall frames with braces on one side and only a stud on the other. The sides with the studs only are facing each other to form a party wall. The base and intermediate frames have braced wall frames 260 on the outside and the studs 261 on the inside to form the party wall. In the top frames 254 the equivalent wall frames are indicated by the numerals 270 and 271.

[0084] The wall frames which adjoin to form the party wall may in various examples only have one vertical stud and / or may have fewer braces than the side which is not forming a party wall. In other examples, the inside wall frames are the same as the outside ones to provide a double thickness party wall for enhanced thermal and sound insulation.

[0085] There the terrace has more than two, internal structures may have wall frames on both sides with less bracing than the outside wall frames.

[0086] Attaching units together in terraced or duplex form creates a very strong set of buildings, especially suitable for seismic and wind zones. This can be achieved by reducing wall thickness and mirroring units.

[0087] Referring to Fig. 7 another example, 300, is shown, having: a base frame 301, with structural wall and ceiling frames; an intermediate frame 302 akin to the base frame 301, thereby providing additional structural strength as compared to only opposed wall frames, and a top frame 303 with structural wall frames and a roof truss 304 with parallel members 305 and 306 joined by vertical studs 307 and braces 308.

[0088] Referring to Fig. 8, connections between structural members can be made with excellent structural integrity by use of nail plates spanning members, most often horizontally and vertically. This example is that on one side between the base and intermediate frames 301 and 302, and the nail plates are indicated by the numerals 319, 320, 321, and 322. Ends of vertical studs are advantageously joined to both cross members and to horizontal members of the lowermost frame by hold down brackets 324, each having an L-shaped nail plate 323 and a bolt 325 extending down into the horizontal member of the other frame. In this case the bolt extends through a subfloor 330 of sheeting material across the tops of the base frames 301.

[0089] The use of LVL material (engineered lumber) can increase the strength of the portal frames by a significant margin and is a common material in the supply chain.

[0090] Components of embodiments can be employed in other embodiments in a manner as would be understood by a person of ordinary skill in the art. The invention is not limited to the embodiments described but may be varied in construction and detail.

Claims

Claims1. A method of constructing a multi-storey building frame comprising the steps of: placing a series in a longitudinal direction of portal base frames (1, 11) in vertical position, at least some of the base frames each comprising: a pair of opposed wall frames (2, 3), a structural ceiling frame (4, 14), and a lower tie (5) or structural frame (15) spanning the wall frames at or near ground level; securing horizontal sheeting (103) to the base frames across the tops of the base frames; interconnecting at least some of said base frames in the longitudinal direction by strongback braces, placing a series in the longitudinal direction of portal top storey frames (21, 31, 41) over the sheeting in vertical position to form a frame for a top storey and a roof, each said top storey frame comprising: a pair of opposed wall frames (22, 23, 32, 33, 42, 43), a roof truss (24, 34, 44)), and a lower tie (25, 45) or structural frame (35) spanning the wall frames; and interconnecting at least some of said top storey frames in the longitudinal direction by strongback braces.

2. A method as claimed in claim 1, wherein opposed wall plates (104) are secured to the sheeting (103) and the top storey frames are placed on and span said wall plates.

3. A method as claimed in claim 2, wherein each wall plate (104) comprises a pair of parallel rails.

4. A method as claimed in any preceding claim, wherein the base frames are interconnected by strongback structural members.

5. A method as claimed in any preceding claim, wherein the top storey frames are interconnected by strongback structural members.

6. A method as claimed in any preceding claim, wherein the top storey frames (21, 41) form a second storey or a mezzanine and they are placed directly on said sheeting.

7. A method as claimed in any of claims 1 to 5, wherein the building is a three-storey building, and an intermediate storey is formed by placing intermediate frames (51) on said sheeting, interconnecting said intermediate frames in the longitudinal direction, and placing the top storey frames on said intermediate frames.

8. A method as claimed in any preceding claim wherein each of the base frame wall frames comprises a plurality of studs (6, 7) and at least one brace (8).

9. A method as claimed in claim 8, wherein there is at least one intermediate stud in at least some base frame wall frames.

10. A method as claimed in any preceding claim, wherein at least some of the top storey frame wall frames each comprises plurality of studs (6, 7) and at least one brace (8).

11. A method as claimed in any preceding claim, comprising the further steps of pouring a concrete base (101) on a foundation, placing at least a pair of opposed wall plates (102) on the concrete base, and the base frames are placed on the concrete base and are secured to the wall plates (102).

12. A method as claimed in claim 11, wherein each wall plate on the concrete base comprises a pair of rails (102).

13. A method as claimed in any preceding claim, wherein a space for a stairwell is provided by choosing a desired longitudinal spacing between two successive base frames to accommodate the stairwell.

14. A method as claimed in any of claims 7 to 13, wherein cross members are secured to at least some of the intermediate frames before erection of the top storey frames.

15. A method as claimed in any preceding claim, wherein at least some base frames (1) are each provided joined to an upper frame (41), either an intermediate frame or a top frame, by hinges (201), and they are folded to be co-planar on site.

16. A method as claimed in any preceding claim, comprising the further steps of erecting on site at least two multi-storey building frames (250) laterally arranged side-by-side, with adjoining wall frames (261, 271) forming a party wall frame.

17. A method as claimed in claim 16, wherein the wall frames (261, 271) which form the party wall frame have less bracing than wall frames (260, 270) for an external wall.

18. A method as claimed in any preceding claim, wherein at least some adjoining structural members of adjoining frames are joined by spanning nail plates.

19. A method as claimed in any preceding claim, wherein at least one pair of upper and lower adjoining frames (302, 301) one atop the other are joined by a hold down bracket (324) with an L-shaped nail plate (323) and a bolt (325) extending vertically through the nail plate, a structural member of one frame, and a structural member of the adjoining frame.

20. A method as claimed in claim 19, wherein said bolt extends through sheeting (330) over the lower frame.

21. A kit for manufacture of a building frame, the kit comprising: a plurality of portal base frames (1, 11), at least some of the base frames each comprising: a pair of opposed wall frames (2, 3), a structural ceiling frame (4, 14), and a lower tie (5) or structural frame (15) spanning the wall frames at or near ground level; horizontal sheeting (103) configured to fit to the base frames across the tops of the base frames; a plurality of portal top storey frames (21, 31, 41) to form a frame for a top storey and a roof, each said top storey frame comprising: a pair of opposed wall frames (22, 23, 32, 33, 42, 43), a roof truss (24, 34, 44)), and a lower tie (25, 45) or structural frame (35) spanning the wall frames.

22. A method of constructing a two-storey building frame (200) comprising the steps of:(a) placing a series in a longitudinal direction of portal base frames in vertical position, at least some of the base frames each comprising:a pair of opposed wall frames, and a lower tie or structural frame spanning the wall frames at or near ground level;(b) either before or after step (a) folding out around hinges a portal top storey frame from each base frame to form a frame for a top storey and a roof, each said top storey frame comprising: a pair of opposed wall frames, a roof truss, and a lower tie or structural frame spanning the wall frames; and (c) interconnecting at least some of said base frames in the longitudinal direction by strongback braces and interconnecting at least some of said top storey frames in the longitudinal direction by strongback braces.

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